Field facet mirror for an illumination optics of a projection exposure apparatus for EUV microlithography

ABSTRACT

A field facet mirror for an illumination optics of a projection exposure apparatus for EUV microlithography transmits a structure of an object arranged in an object field into an image field. The field facet mirror has a plurality of field facets with reflection surfaces. The arrangement of the field facets next to one another spans a base plane. Projections of the reflection surfaces of at least two of the field facets onto the base plane differ with respect to at least one of the following parameters: size, shape, orientation. A field facet mirror results which can ensure a uniform object field illumination with a simultaneously high EUV throughput.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of, and claims benefit under 35 USC 120to, U.S. application Ser. No. 13/034,275, filed Feb. 24, 2011, which isa continuation of, and claims benefit under 35 USC 120 to, internationalapplication PCT/EP2009/006290, filed Aug. 31, 2009, which claims benefitunder 35 USC 119 of German Application No. 10 2008 049 586.7, filed Sep.30, 2008 and under 35 USC 119(e) of U.S. Ser. No. 61/101,445, filed Sep.30, 2008. U.S. application Ser. No. 13/034,275 and internationalapplication PCT/EP2009/006290 are hereby incorporated by reference intheir entirety.

FIELD

The disclosure relates to a field facet mirror for an illuminationoptics of a projection exposure apparatus for EUV microlithography. Thedisclosure also relates to a method for producing a field facet mirrorof this type, an illumination optics with a field facet mirror of thistype, an illumination system with an illumination optics of this type, aprojection exposure apparatus with an illumination system of this type,a method for producing a microstructured or nanostructured componentusing a projection exposure apparatus of this type, and a componentwhich is microstructured or nanostructured and produced according to aproduction method of this type.

BACKGROUND

A field facet mirror for use in an illumination optics of a projectionexposure apparatus for EUV microlithography is known from WO2007/128407A.

Often, field facet mirrors of this type should, on the one hand, provideuniform illumination of the object field and, on the other hand, guideas large a faction as possible of the illumination light produced by anEUV light source to the object field. In this case, the facets of thefield facet mirror receive a shape and an aspect ratio, which areadapted to the object field to be illuminated. There is still a desirefor improvement in the known field facet mirrors in relation to thesimultaneous ensuring of a uniform object field illumination, inparticular when the illumination light provided by the EUV light sourcedoes not have a uniform intensity distribution over the illuminationbundle, and a high EUV throughput.

SUMMARY

The disclosure provides a field facet mirror for use in an illuminationoptics of a projection exposure apparatus for EUV microlithography thatcan ensure a uniform object field illumination with a simultaneouslyhigh EUV throughput.

The disclosure discusses giving up the previously maintained boundarycondition, according to which the projection of field facet edges in thedirection of a normal of a support plate generally present of the knownfield facet mirrors is identical, and specifically identical both inrelation to the size and also the shape and also in relation to theorientation. Owing to the new degree of freedom of permittingnon-identically formed projections, a pre-compensation, for example, ofa possible rotation of the images, because of the imaging conditions, ofindividual field facets relative to one another can be achieved duringtheir superimposition on the object field. A rotation of this type ofthe facet images results, as is recognised according to the disclosure,because of various paths of the illumination light guided channel-wisevia the field facets through the illumination optical system. Avariation in the imaging scale of the field facets on the object fieldmay also occur here. By giving up the condition of identical projectionsof the field facet reflection surfaces onto the base plane, thisvariation of the imaging scale may also be pre-compensated. During theimaging onto the object field, the rotation of the facet images withoutpre-compensation leads to the undesired effect of edge scattering of theobject field illumination as the images of the field facets superimposedon the object field no longer match the different real facet faces, inparticular at the edge. The base plane of the field facet mirror, whichis spanned by the field facets arranged next to one another, isgenerally predetermined by a holding plane of a field facet support.This base plane generally coincides with a main reflection plane of thefield facet mirror, relative to which the field facets can still bearranged tilted individually for the allocation of illumination channelsof the illumination optical system. The main reflection plane is in thiscase the reflection plane with untilted field facets (field facetsaligned with the holding plane).

The field facets may be arranged next to one another on a support plate.This support plate then generally runs parallel to the base plane of thefield facet mirror.

At least two of the field facets may be arranged tilted with respect toone another by more than 1° about an axis perpendicular to the baseplane of the field facet mirror. The tilting relative to an untiltedstarting position may, for example, be in the range between −3° and 3°,in the range between −2° and 2° or in the range between −1° and 1°. Thistilting at most changes the tilting position of the reflection surfacesof the field facets slightly and thus has no or slight effects on theallocation of the tilted field facet to the illumination channels of theillumination optical system. Such a tilted arrangement of the fieldfacets represents a degree of freedom which was previously rejectedbecause of assumed steric accommodation problems of the field facets andwhich helps to reduce or even completely avoid an edge scattering of theobject field illumination observed in the previously known occupationgeometries of field facets on the field facet mirror. The degree offreedom according to the disclosure of the tilting of the field facetsabout an axis perpendicular to the base plane or to the main reflectionplane facilitates a design in which tilting angles about axes, which liein the main reflection plane and lead to too great a maladjustmentbetween the face of the projection of the reflection surfaces of tiltedfield facets on the main reflection plane, on the one hand, and the realreflection face, on the other hand, are avoided. According to thedisclosure, field facets with a more favourable aspect ratio in relationto their manufacturing can be used to occupy the field facet mirror,without a disruptive edge scattering in the object field illuminationresulting. In addition, the degree of filling of the object field andtherefore the transportable light conductance are thus effectivelyincreased. This is important, in particular for sources with a largelight conductance or for illumination systems, which offer illuminationpupils which are filled to a different degree without light loss. Anallocation of field facets tilted about the tilting axis perpendicularto the main reflection plane to the illumination angles predetermined byan allocation to pupil facets of a pupil facet mirror leads to thepossibility of ensuring an intensity monitoring of the illuminationlight taking place at the edges of the object field with minimisedlosses. Field facets of this type may be used in a projection exposuresystem, within which, during a projection exposure, an object isdisplaced continuously or step-wise in an object displacement direction.

A part ring or arc shape of the field facets can allow well adaptedillumination of a correspondingly part ring-shaped or arcuate objectfield. An object field shape of this type can be imaged well with adownstream projection optical system of the projection exposureapparatus designed as a mirror optical system.

An arrangement of the tilting axis can ensure that a tilting of therespective field facet only slightly changes the occupation requirementof this field facet in the main reflection plane, as a tilting at bestleads to a slight deviation of the position of the arcuate or partring-shaped side edges of the facet reflection face. During a tiltingabout this tilting axis, the end faces of the facet reflection surfacesleading or following in the peripheral direction about the partialcircle or arc shape are practically exclusively displaced.

Field facets can be manufactured with a lower production outlay incomparison to field facets with a small part ring thickness. Thisminimal part ring thickness is accompanied by a thickness, which isaccordingly easier to handle for the production of the field facets, ofthe respect field facet base body. In addition, the relative mutualshading of the field facets with increasing width may be less.

Field facets tilted about a further degree of tilting freedom can ensurea desired variability in the allocation of the field facets to pupilfacets of a pupil facet mirror of an illumination optics of the EUVprojection exposure system. A predetermined and well mixed allocation ofpupil facets of the pupil facet mirror allocated to the field facets ispossible. An axis is selected as the tilting axis for the further degreeof tilting freedom, the tilting of which leads to as small a deviationas possible of a face of a field facet projected onto the mainreflection plane from on the real reflection surface of the field facet.

Facet base bodies limited by opposing spherical side walls may beproduced precisely. “Spherical” in this context means “shaped like thesection of a face of a ball”. Alternatively, the field facets may alsohave facet base bodies, which are limited by two cylindrical side wallswhich are opposing and displaced in parallel, in particular, withrespect to one another. It is possible to arrange field facets of thistype next to one another with small spacings, which leads to a highoccupation density of the field facets within the main reflection plane.

A facet shape can be well matched to an arcuate or part ring shape of anobject field to be illuminated. One of the two opposing spherical sidewalls is convex and the other of the two spherical side walls isconcave.

Facets with side walls of the facet base body may, on the one hand, beclosely packed and, on the other hand, allow a displacement of the twoadjacent facet base bodies relative to one another along the sphericalface of the two mutually facing side walls. This allows new degrees offreedom in the relative positioning of the field facets of the fieldfacet mirror with respect to one another.

Field facets can be produced with one and the same processing tool forproducing the spherical side walls.

Facet mirrors can be packed closely, on the one hand, and, on the otherhand, can be arranged closely packed between other field facets andnevertheless be tilt-adjusted about the centre.

Field facets may also be adapted to more exotic object field forms orelse to other requirements, for example to control the intensity of theillumination light.

A field facet mirror can allow the illumination of sensors arranged inthe region of edges of the object field, so an effective monitoring ofthe energy or intensity of a light source, with which the facet mirroris loaded, is possible.

Field facets which are adjacent and tilted with respect to one anothercan have advantages which correspond to those of a field facet mirror.

Intermediate spaces can allow an individual arrangement of theindividual field facets and thus good compensation of an undesired imagetilting effect in the imaging of the field facets in the object field.The field facets may be arcuate or rectangular in design. The fieldfacets may be arranged column-wise in the base plane of the field facetmirror. Packing densities of the field facets are possible, which aregreater than 50%.

A field facet mirror, for which, according to the disclosure, variousembodiments are given, can increase the EUV light throughput inside aprojection exposure apparatus equipped with a field facet mirror of thistype.

A manufacturing process can allow efficient production of field facetgroups with side walls of adjacent facet base bodies, which have thesame radius of curvature.

A manufacturing method can be adapted to facet block arrangements offield facet mirrors.

A manufacturing method can allow an exact orientation of the fieldfacets assembled within a facet block.

The advantages of an illumination optics can correspond to those whichhave already been discussed above with reference to the field facetmirror according to the disclosure. It was recognised in theillumination optics, that the departure from the adjustmentspecification for the transmission facet mirrors, to in each casesuperimpose the centres of the field facet images in the object field,can lead to further degrees of freedom with regard to the optimisationof the total superimposition of the field facet images in the objectfield. The adjustment of the transmission facets takes place such thatthe superimposition of the facet images is optimised in total over theobject field. The field facets and the associated transmission facetsmay be static facets or else actuatable facets, in other words facetswhich can be displaced in a controlled manner. The field facets and/orthe transmission facets may be constructed from a plurality ofindividual facets. These individual facets may be displaceable, in amanner which is actuatable, relative to one another. A correspondingconcept with an individual facet/individual mirror structure of thistype is known from DE 10 2008 009 600 A. By displacing or tilting of thefield facets, the transmission facet individually associated with arespective field facet may be selected from a plurality of possibletransmission facets of the transmission facet mirror. The extendedregion in the centre of the object field, on which the centres of thereflection surfaces of the field facets are imaged in the illuminationoptics according to the disclosure, may take in an area in the order ofmagnitude of one or more mm². The extended region has an area, which isspanned by a dimension extending approximately tangentially to theimages of the arcuate field facets and a dimension extendingapproximately radially to the images of the arcuate field facets. Thetangential dimension may extend in the direction of a long field extentof the object field and the radial dimension may extend along a shortfield extent of the object field. The tangential dimension has a size,which is proportional to an arc radius of curvature of the images of thefield facets and to the tangent (tan) of a tilting angle of the fieldfacets relative to one another about an axis perpendicular to the baseplane of the field facet mirror. In the case of typical tilts of thistype of the field facets in the range of ±3° and an arc radius ofcurvature of the field facet images of 150 mm, a tangential dimension isproduced of the extended region of 15 mm. The radial dimension of theextended region is proportional to a spacing of the object plane from atarget superimposed plane spaced apart therefrom, of the field facetimages. This target superimposition plane may coincide, for example,with a displacement plane of a correction diaphragm. A UNICOM may bearranged, for example, in the target superimposition plane. The targetsuperimposition plane is also called below a diaphragm or stop plane ofa correction diaphragm or stop. In addition, the radial dimension of theextended region is proportional to a numeric aperture of the objectfield illumination. Assuming typical values for the numerical apertureof the object field illumination, for example NA=0.1, and for thespacing between the object plane and the target superimposition plane,for example 10 mm a value of 1.5 mm is produced for the radial dimensionof the extended region.

The extended region may have an extent of between 3 mm and 25 mm, inparticular between 5 mm and 20 mm, for the tangential dimension. For theradial dimension, the extended region may have an extent of between 0.5mm and 3 mm, in particular between 0.75 mm and 2 mm. As the objectplane, on the one hand, and the target superimposition plane, on theother hand, are closely adjacent to one another, it is unimportant inpractice in considering the dimension above, whether the extended regionis observed in the target superimposition plane or in the object plane.

In an illumination optics, via the orientation of the transmissionfacets to image the centres of the reflection surfaces of the fieldfacets onto a region extended along the long field extent in the centreof the object field, a compensation of a tilting effect of the imagingof arcuate field facets into the object field can surprisingly beachieved. According to the disclosure, it was recognised that a tiltedarc is also still very similar to the original arc if the condition isgiven up that all the centres of the facet arcs in the object field haveto be precisely imaged on one another. With surprisingly little outlay,good compensation of a tilting imaging effect of the following opticalsystem is produced without a relatively large intervention into thestructure of a conventional field facet mirror with curved field facetsbeing used for this purpose.

A superimposition arrangement can allow the use of a correctionmechanism influencing the intensity of the object field illuminationfrom the more sharply superimposed edge, so an undesired effect on anillumination angle distribution when using this correction mechanism isminimised. The superimposition may be optimised in the object plane oralternatively also in a displacement plane of the correction mechanism,which does not have to coincide with the object plane.

The advantages of an illumination system, a projection exposureapparatus, a production method, and a microstructured component cancorrespond to those which were already discussed above with reference tothe field facet mirror according to the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the disclosure will be described in more detail belowwith the aid of the drawings, in which:

FIG. 1 schematically shows a projection exposure apparatus for EUVmicrolithography, an illumination optics being shown in meridionalsection;

FIG. 2 shows a plan view of a field facet mirror of the illuminationoptics according to FIG. 1;

FIG. 3 schematically shows a detail enlargement according to the detailIII in FIG. 2;

FIG. 4 shows an individual one of the field facets of the field facetmirror according to FIG. 2, enlarged, perspectively and broken;

FIGS. 5 to 8 in each case show a plan view of various embodiments offield facets arranged group-wise for use in the field facet mirroraccording to FIG. 2 and examples of the adjacent arrangement thereof;

FIG. 9 shows illumination conditions at the edge of an object fieldilluminated by the illumination optics at the site of an intensitymonitoring sensor in a meridional section comparable to FIG. 1 rotatedthrough 180° about an x-axis and through 90° about a z-axis;

FIG. 10 shows a plan view of the object field, the edge illuminationthereof being emphasised for various illumination directions;

FIG. 11 shows a superimposition of the illumination of the object fieldproceeding from a predetermined test point pattern onto the field facetsin an arrangement according to FIG. 2 in a view similar to FIG. 10;

FIG. 12 schematically shows a view of two field facets which areadjacent and arranged tilted with respect to one another to showpossible tilting angles;

FIG. 13 schematically shows a sequence in the production of a fieldfacet mirror with field facets, side walls facing one another ofadjacent facet base bodies having the same radius of curvature;

FIG. 14 shows a further embodiment of a field facet mirror for use inthe illumination optics according to FIG. 1 in a view similar to FIG. 2;

FIG. 15 shows a detail enlargement according to the detail XV in FIG.14;

FIG. 16 shows a further embodiment of a field facet mirror for use inthe illumination optics according to FIG. 1 in a view similar to FIG. 2;

FIG. 17 shows the detail XVII from FIG. 16, enlarged;

FIG. 18 shows a superimposition of the illumination of the object fieldby a further embodiment of an illumination optics with a field facetmirror, the reflection surfaces of which are imaged by a transmissionfacet mirror configured as a pupil facet mirror, in a superimposedmanner, into the object field in a view similar to FIG. 11, in a targetsuperimposition plane of a correction diaphragm or stop; and

FIG. 19 shows the positions of the images of centres of the reflectionsurfaces of the field facets of the illumination optics according toFIG. 18 in the object field to a scale which is sharply enlargedcompared to the view according to FIG. 18.

FIG. 1 schematically shows a projection exposure apparatus 1 for EUVmicrolithography. An EUV radiation source is used as the light source 2.This may be an LPP (laser produced plasma) radiation source or a DPP(discharge produced plasma) radiation source. The light source 2 emitsEUV useful radiation 3 at a wavelength in the range between 5 nm and 30nm. The useful radiation 3 will also be called illumination or imaginglight below.

The illumination light 3 emitted by the light source is firstlycollected in a collector 4. This may be, depending on the type of lightsource 2, an ellipsoidal mirror or a nested collector. After thecollector, the illumination light 3 passes through an intermediate focusplane 5 and then impinges on a field facet mirror 6, which will bedescribed in detail below. From the field facet mirror 6, theillumination light 3 is reflected toward a pupil facet mirror 7. Theillumination light bundle is divided into a plurality of illuminationchannels via the facets of the field facet mirror 6, on the one hand,and the pupil facet mirror 7 on the other hand, one pair of facets witha field facet or a pupil facet being precisely allocated to eachillumination channel.

A following optics 8 arranged downstream of the pupil facet mirror 7guides the illumination light 3, in other words the light of all theillumination channels, toward an object field 9. The field facet mirror6, the pupil facet mirror 7 and the following optics 8 are components ofan illumination optics 10 for illuminating the object field 9. Theobject field 9 is arcuate or part circle-shaped or part ring-shaped, aswill be described below. The object field 9 lies in an object plane 11of a projection optics 12, which is arranged downstream of theillumination optics 10, of the projection exposure apparatus 1. Astructure arranged in the object field 9 on a reticle, not shown in thedrawing, in other words on a mask to be projected, is imaged by theprojection optics 12 on an image field 13 in an image plane 14. A wafer,also not shown in the drawing, onto which the structure of the reticleis transmitted to produce a microstructured or nanostructured component,for example a semiconductor chip, is arranged at the site of the imagefield 13.

The following optics 8 between the pupil facet mirror 7 and the objectfield 9 has three further EUV mirrors 15, 16, 17. The last EUV mirror 17before the object field 9 is designed as a mirror for grazing incidence.In alternative embodiments of the illumination optics 10, the followingoptics 8 may also have more or less mirrors or even be dispensed withcompletely. In the latter case, the illumination light 3 is guided fromthe pupil facet mirror 7 directly to the object field 9.

To facilitate the illustration of the position relationships, anxyz-coordinate system is used below. In FIG. 1, the x-direction runsperpendicularly to the plane of the drawing into the latter. They-direction, in FIG. 1, runs to the right and the z-direction runsdownward in FIG. 1. If in FIG. 2 et seq. a Cartesian coordinate systemis also used, this in each case spans the reflection surface of thecomponent shown. The x-direction is then parallel to the x-direction inFIG. 1 in each case. An angle relationship of the y-direction of theindividual reflection surface to the y-direction in FIG. 1 depends onthe orientation of the respective reflection face.

FIG. 2 shows the field facet mirror 6 in more detail. This has a totalof four individual field facets 18 arranged in columns S1, S2, S3, S4,which are numbered consecutively from the left to the right in FIG. 2.The two central columns S2 S3 are separated from one another by aninstallation space 19, which runs in the y-direction and has a constantx-extent. The installation space 19 corresponds to a remote fieldshading of the illumination light bundle, which is structurally causedby the structure of the light source 2 and the collector 4. The fourfacet columns S1 to S4 in each case have a y-extent, which ensures thatall four facet columns S1 to S4 are within a circularly limited remotefield 20 of the illumination light 3. The edge of a support plate 21 forthe field facets 18 coincides with the edging of the remote field 20.

Reflection surfaces 22 of the field facets 18 have an arcuate or partring shape congruent to one another, in relation to a projection ontothe xy-plane, in other words in relation to a main reflection plane ofthe field facet mirror 6, which is similar to the shape of the objectfield 9.

The object field 9 has an x/y-aspect ratio of 13/1. The x/y-aspect radioof the field facets 18 is greater than 13/1. Depending on theconfiguration, the x/y-aspect ratio of the field facets 18 is 26/1, forexample, and is generally greater than 20/1.

In total, the field facet mirror 6 has 416 field facets 18. Alternativeconfigurations of field facet mirrors 6 of this type may have numbers offield facets 18 in the region of between a few tens and a thousand, forexample.

The field facets 18 have an extent in the y-direction of about 3.4 mm.The extent of the field facets 18 in the y-direction is, in particular,greater than 2 mm.

The total of all the 416 field facets 18 has a packing density of 73%.The packing density is defined as the sum of the illuminated reflectionsurfaces 22 of all the field facets 18 in relation to the faceilluminated in total on the support plate 21.

FIG. 3 shows a detail enlargement of the field facet mirror 6 in an endregion of the facet column S1. Adjacent field facets 18 are arrangedtilted with respect to one another by more than 1° about an axis, whichruns perpendicular to the main reflection plane of the field facetmirror 6, in other words parallel to the z-axis in FIG. 2.

This is shown in FIG. 2 using the example of the second field facet 18 ₂from the bottom in the facet column S4 in comparison to the third fieldfacet 18 ₃ from the bottom in column S4. These two field facets 18 ₂, 18₃ are tilted with respect to one another about a tilting angle Kz ofabout 2° about an axis 23, which is perpendicular to the plane of thedrawing of FIG. 2, in other words perpendicular to the main reflectionplane of the field facet mirror 6. A larger tilting angle Kz is alsopossible. This means that the field facet 18 ₂ projects relative to thefield facet 18 ₃ at the left-hand edge, in other words projects in thenegative x-direction, while the field facet 18 ₃ projects relative tothe field facet 18 ₂ by the same amount at the right-hand edge, in otherwords in the positive x-direction. Corresponding projections betweenadjacent field facets 18 can be inferred from the detail enlargement ofFIG. 3. The tilting angle Kz between adjacent field facets 18 vary inthe range between ±3°.

The tilting axes 23, by which the tilting angle Kz of respectivelyadjacent field facets 18 is defined with respect to one another arelocated centrally between the ring centres which are allocated to thesetwo part ring-shaped field facets 18. The adjacent field facets 18 arethus tilted with respect to one another about the axis 23, whichapproximately coincides with the ring centres. The tilt of adjacentfield facets 18 with respect to one another about the axis 23 definedvia the position of the respective ring centres of these field facets 18is also designated the tilt Z below. A tilting angle Kz is allocated tothis tilt Z in each case.

FIG. 4 shows details of the structure of one of the field facets 18. Thereflection surface 22 in the x-direction has an extent of about 60 mm.The facet base body 24 continues remote from the reflection surface 22in the manner not shown in more detail in FIG. 4.

The reflection surface 22 has a multilayer coating, which increases thereflectivity, with alternating molybdenum and silicon layers.

The facet base body 24 is convexly/concavely limited by two opposingspherical side walls 27, 28, arranged substantially perpendicular to they-axis. The side wall 27 facing the observer of FIG. 4 is convex and theopposing side wall 28 remote from the observer of FIG. 4 is concave.

If one is limited to a design of this type of a facet base body 24, inwhich the side walls 27, 28 are cylinder faces displaced in parallel,projections of the reflection surfaces 22 of facet base bodies 24 ofthis type onto a base plane xy, which is spanned by the arrangement ofthe field facets 18 next to one another, are limited by part circlesdisplaced in parallel. The direction of the radially extending paralleldisplacement of the inner part circle defined by the concave side wall28 to the outer part circle defined by the convex side wall 27 isindividual for each of the field facets 18. An angle between theseparallel displacement directions and the y-axis corresponds to therespective tilting angle Kz. The side walls 27, 28 of the facet basebody 24 may also be spherical faces displaced in parallel.

The reflection surface 22 is configured as one of a total of four endwalls of the facet base body 24. The reflection surface 22 may be planaror else, in accordance with predetermined imaging specifications,curved, for example spherical, aspherical or as a freeform face.

FIG. 4 shows a further tilting possibility of adjacent field facets 18with respect to one another, namely a tilting about a further tiltingaxis 25 parallel to the y-axis, which will also be called the tilt Ybelow. The tilting axis 25 runs parallel to a radius, which ispredetermined by the part ring shape of the reflection surface 22 of thefield facet 18. Because of the tilt Y, there is an angle deviation of anormal N to the tilted reflection surface (cf. 22′) in FIG. 4. This tiltY deviation about a tilt angle Ky is shown very exaggerated in FIG. 4. Atilt Y of this type can be used for the correct orientation of thereflection surface 22 of the respective field facet 18 or also inconjunction with the production of the field facet mirror 6. Inprinciple, it is possible via the tilt Y to being about an allocation ofthe respective field facet 18 to the associated pupil facet of the pupilfacet mirror 7.

As an alternative to a tilt about a tilting angle Kz, as described inconjunction with FIG. 2, it is also possible to tilt the field facets 18about a tilting axis 26 also parallel to the z-axis (cf. FIG. 4), whichalso extends through a centre 27 a of the reflection surface 22. Atilting of this type about the tilting axis 26 also leads to a tilt Z ofthe field facet 18.

FIG. 5 again schematically shows the tilting of adjacent field facets 18about the tilting axes 23 respectively defined with respect to these.Sections of two adjacent columns Sx and Sy are shown in FIG. 5. Intotal, four field facets 18 ₁ to 18 ₄ of the column Sx, the index ofwhich is numbered consecutively from the top to the bottom, and a totalof three field facets 18 ₅ to 18 ₇ of the column Sy, the index of whichis also numbered consecutively from the top to the bottom, are shown inFIG. 5. The field facets 18 ₁ to 18 ₇ each in turn have an arcuate orpart ring-shape.

Not all the field facets 18 ₁ to 18 ₇ in relation to their projectiononto the main reflection plane xy of the field facet mirror 6 have apart ring-shape which is congruent to one another. Thus, the field facet18 ₂ passes over a larger peripheral angle than the field facet 18 ₁arranged thereabove and has a larger extent in the x-direction than thefield facet 18 ₁.

Mutually facing side walls 27, 28 of the field facets 18 ₁ to 18 ₄, onthe one hand, and of the field facets 18 ₅ to 18 ₇ on the other hand, ineach case have the same radius of curvature.

Effective tilting angles Kz of the field facets 18 ₅ to 18 ₇ withrespect to one another are indicated in FIG. 5 by arrows 29. Three ofthe arrows 29 shown are extensions of the centre symmetry radii of therespective field facets 18 ₅ to 18 ₇. The respective centre symmetryradius is the coinciding radius of the two concave or convex side walls28, 27 of one of the field facets 18. These symmetry radii are alsocharacterised by the reference numeral 29 in the drawing. Arepresentative tilting axis 23 is also shown.

The radii of curvature of some of the side walls 27, 28 of the fieldfacets 18 are indicated by dashed circles in FIG. 5.

FIG. 6 shows a further arrangement of adjacent field facet mirrors 18 ₁to 18 ₈ within a facet column Sx. The spherically concave side wall 28 ₈of the field facet 18 ₈ shown at the very bottom in FIG. 6 has a radiusof curvature with the amount R₁, proceeding from a centre 30 ₈. Thespherically convex side wall 27 ₈ of the field facet 18 ₈ has a radiusof curvature, also with the amount R₁, proceeding from a centre 30 ₇,which is arranged offset with respect to the centre 30 ₈ about a centrethickness Mz of the facet base body 24 ₈ of the field facet 18 ₈ in thepositive y-direction. The centre 30 ₇ is simultaneously the centre forthe curvature of the concavely spherical side wall 28 ₇ of the fieldfacet 18 ₇, which is adjacent to the field facet 18 ₈. Accordingly, theother side walls 27 ₁ to 27 ₇ and 28 ₁ to 28 ₆ of the other field facets18 ₁ to 18 ₈ shown in FIG. 6 are also defined by centres 30 ₁ to 30 ₇which are in turn spaced apart from one another in each case by thespacing Mz in the positive y-direction.

Thus, in the embodiment according to FIG. 6, all the side walls 27 ₁ to27 ₈, 28 ₁ to 28 ₈ with regard to amount have the same radius ofcurvature R₁. The side walls 27 _(x), 28 _(x) of one of the facetmirrors 18 _(x), in the embodiment according to FIG. 6, do not runconcentrically, but the centre points 30 _(x) of curvature of the twoside walls 27 _(x), 28 _(x) of the respective field facet mirror 18 _(x)are offset with respect to one another by the thickness of thereflection surface in the y-direction. FIG. 7 shows an alternativeembodiment of field facets 18 arranged adjacent within a column S. InFIG. 7, four field facets 18 ₁ to 18 ₄ are shown above one another. Twoof the four field facets 18 shown in FIG. 7, namely the field facets 18₂ and 18 ₄ have opposing side walls 27 ₂, 28 ₂ or 27 ₄, 28 ₄, which havedifferent radii R₂, R₁ of curvature and are concentric. This isillustrated in more detail in FIG. 7 with the aid of the curvature ofthe side walls 27 ₂, 28 ₂ of the field facet 18 ₂. The sphericallyconcave side wall 28 ₂ has a radius of curvature with the amount R₁,proceeding from a centre 30 ₂. Proceeding from the same centre 30 ₂, thespherically convex side wall 27 ₂ of the field facet 18 ₂ has a radiusof curvature with the amount R₂, R₂ being greater than R₁.

The two further field facets 18 ₁, 18 ₃ shown in FIG. 7 haveconvex/concave side walls 27 ₁, 28 ₁ or 27 ₃, 28 ₃, which have differentradii of curvature and are in addition not concentric. The arrangementof the facets 18 _(x) in the column Sx according to FIG. 7 is such that,in each case, a field facet 18 with concentric side walls 27, 28alternates with a field facet 18 with non-concentric side walls 27, 28,which also have different radii of curvature.

FIG. 8 shows a facet column Sx with field facets 18 ₁ to 18 ₄, theopposing side walls 27, 28 of which are not concentric. In addition,centres, by which the spherical side walls 27, 28 of the field facets 18₁ to 18 ₄ according to FIG. 8 are defined, are also offset with respectto one another in the x-direction, from case to case. The reflectionsurfaces of the field facets 18 ₁ to 18 ₄ according to FIG. 8 in eachcase form part rings with a y-thickness varying in the peripheraldirection. The y-thickness of the reflection surface 22 of the fieldfacet 18 ₄ in FIG. 8 increases continuously from the left to the right.The y-thickness of the reflection surface 22 of field facet 18 ₂ in FIG.8 decreases continuously from the left to the right. Thicknesses of thefield facets 18 ₁ to 18 ₄ in the y-direction are shown sharplyexaggerated in FIG. 8. Lines running at an acute angle to the x-axis andrepresenting the tilting angle Kz of the field facets 18 ₁, 18 ₂ and 18₃ are indicated by dashed lines in FIG. 8.

Illumination conditions in the region of the object field 9 and in theregion of the object plane 11 will be described below with the aid ofFIGS. 9 to 11. Arranged in a detection plane 31, which is spaced apartfrom the object plane 11 by a spacing Δz and lies in the beam directionof the illumination light 3 upstream of the object plane 11, is adetection device 32 with two EUV intensity sensors 33 of which one isshown schematically in FIG. 9. FIG. 9 shows, in an enlarged manner, theedge of the object field 9 in the case of positive x-values.

To illuminate the object field 9, the latter can be used independentlyof an illumination angle within the numeric aperture NA of theillumination light 3 up to an x-value x_(n) for projection exposure.With radiation from the direction −NA the sensor 33 shown in FIG. 9shades the object field 9 in the case of x-values, which are greaterthan x_(n). So that the sensor 33 is still acted upon from the beamdirection −NA, the illumination light bundle in the object plane 11 inthe x-direction has to have an extent up to x_(−NA), whereinx_(=NA)>x_(n) applies. So that illumination light 3, which impinges onthe sensor 33 shown in FIG. 9 precisely in the z-direction (v_(x)=0),there has to be an illumination up to the value x₀ in the object plane11, wherein x₀>x_(−NA) applies. So that illumination light which fallsbelow the illumination angle +NA reaches the sensor 33 shown in FIG. 9,an illumination up to the x-value x_(+NA) has to take place in theobject plane 11, wherein x_(+NA)>x₀ applies. This is shown schematicallyin FIG. 10, which shows the illumination of the object field 9 beyondthe edge thereof at values ±x_(n). With different point views, thecorners of the object field illumination required in the x-direction areshown so that an illumination of the sensor 33 is ensured in the case ofradiation from the illuminations direction −NA, v_(x)=0 and +NA. Thecorners with respect to the illumination direction −NA, which in thecase of positive x-values have the smallest x-spacing from the usablefield edge x_(n), in the case of negative x-values, have the greatestx-spacing from the usable field edge −x_(n). In the case of the cornerswith respect to the illumination direction +NA this is precisely thereverse. The corner points with respect to the illumination directionv_(x)=0 on both sides of the object field 9 have the same x-spacing withrespect to the usable field limits ±x_(n).

Accordingly, the field facets 18, the shape of which is superimposedimaged on the object field 9, have to have, as a function of theillumination angle, in other words as a function of the allocationthereof to the respective pupil facets of the pupil facet mirror 7,various extents in the x-direction, so that an illumination of thesensors 33 is in each case just fulfilled without loss of light as afunction of the illumination angle. These various extents of the fieldfacets 18 in the x-direction to illuminate the sensors 33 are achievedby an asymmetry achieved in the x-direction of certain of the fieldfacets 18 about the central symmetry radius in the x-direction.

The illumination of the sensors 33 is thus achieved independently of thetilting angle Kz by an adaptation of the azimuthal extent of theindividual field facets 18 on both sides of the centre symmetry radius29. Measured from the centre symmetry radius, the field facets 18 havean unequal x-extent to either side as well as an unequal extent in theazimuthal direction about the respective tilting axis 23.

In an insert, FIG. 10 shows the shape of the projections of asymmetrisedfield facets 18 a, 18 b and 18 c of this type. All three field facets 18a to 18 c have one and the same centre symmetry radius 29. Proceedingfrom this, the uppermost field facet 18 a shown in FIG. 10 to the rightpasses over a larger azimuth angle than to the left. The field facet 18b shown in the centre in FIG. 10 to the left passes over a largerazimuth angle than to the right. The field facet 18 c shown at the verybottom in FIG. 10 in both directions passes over approximately the sameazimuth angle. Reference is made to the fact that all the three fieldfacets 18 a to 18 c have the same tilting angle Kz.

FIG. 11 shows the superimposition of field facets 18 tilted with respectto one another according to the arrangement of FIG. 2 with tilt Z in theobject field 9. The superimposition is shown of selected illuminationpoints AP, on the one hand, in the region of the centre of therespective field facet 18 and, on the other hand, in the region of thetwo sides of the field facets 18. FIG. 11 shows that the same positionson the various field facets 18 in the arrangement according to FIG. 2 inthe object field 9 are also superimposed in the region of the edges ofthe object field 9 on the same positions.

An undesired scattering, in other words a deviation of the images of thesame facet point of various facets in the object plane 11 does not takeplace.

This practically perfect superimposition of the images of the fieldfacets 18 in the object field 9 is a direct consequence of the fact thatthe projections of the reflection surfaces 22 of the various fieldfacets 18 on the base plane xy differ in at least one of the followingparameters: size of the reflection surfaces 22, shape of the reflectionsurfaces 22, orientation of the reflection surfaces 22. This differenceleads to a pre-compensation, so the individual imaging of the differentreflection surfaces 22 in the object field 9 with the tilting thustaking place, the change in the size thus taking place and the shapechange thus taking place, leads precisely to the perfect superimpositionof the field facets 18 in the object field 9 shown in FIG. 11.

FIG. 12 illustrates the possibilities of a tilting of two field facets18 ₁, 18 ₂, the mutually facing side walls 27 ₁, 28 ₂ of which arearranged concentrically with the same radius of curvature. Any tilt onthe surface defined thereby about a centre O is possible. The associatedtilting axis may run in any direction. This tilting axis runs throughthe centre O.

FIG. 13 schematically shows the sequence of a method for producing afacet mirror 6 in the manner of that of FIG. 2. Firstly, individualcrude field facets 34 with spherical side walls 27, 28 are produced (cf.method step 35, in which a spherical grinding body 36 to produce theside walls 28 is indicated). In a method step 37, the individual crudefield facets 34 are then allocated to a field facet stack 28, in whichrespective mutually associated side walls 27, 28 of adjacent facet basebodies 24 have the same radius of curvature.

The individual reflection surfaces 22 of the crude field facets areprocessed individually, in other words optically polished and providedwith the reflection multi-layer.

After the allocation in step 37 and before the individual processing(step 39) in a method step 40, a block is assembled of the crude fieldfacets 34 (step 40 a) and then a base face 41 of the block of the crudefield facets 34 is ground to a planar reference face. After theindividual processing 39, an assembly of a respective group of the fieldfacets 18 into a facet block 41 then takes place, the reference face 41being placed on a planar counterface 43 of a mirror holding structure44.

A further configuration of a field facet mirror 6 with field facets 18tilted with respect to one another individually in each case about atilt Z is described below with the aid of FIGS. 14 and 15. Components,functions and production method steps, which correspond to those whichwere already described above with reference to FIGS. 1 to 13, have thesame reference numerals and are not discussed in detail again.

The field facet mirror 6 according to FIGS. 14 and 15 has a total of 299field facets 18. The totality of these 299 field facets 18 has a packingdensity of 56%. The packing density, which is also called the degree offilling, relates to the total illuminated surface of the field facetmirror 6. The packing density is produced from the sum of the reflectionsurfaces 22 of the field facets 18 used for reflection divided by thearea of the total and, in the present case, elliptical illumination areaof the field facet mirror 6, which is specified in FIG. 14 by the edgingof the remote field 20. The illumination area without the installationspace 19, in other words without shadings of the remote field 20, whichare caused by components upstream of the field facet mirror 6, isinserted into the denominator of the packing density here.

The basic structure of the field facet mirror 6 according to FIG. 14corresponds, even with regard to the arrangement of the field facets 18in four columns S1 to S4, to the structure of the field facet mirror 6according to FIG. 2. In the field facet mirror 6 according to FIGS. 14and 15, respective adjacent field facets 18 are pivoted (tilt Z) withrespect to one another about a tilting axis 26 running parallel to thez-axis, which extends approximately through the centre 27 a of therespective field facet 18. This is described in more detail below withthe aid of FIG. 15 and two selected field facets 18 ₁, 18 ₂. The fieldfacet 18 ₂ is arranged in the column S2 in FIG. 15 directly below thefield facet 18 ₁. Relative to the field facet 18 ₁, the field facet 18 ₂is arranged tilted about its centre 27 a through about 0.5° counter tothe clockwise direction.

Each of the reflection surfaces 22 of the arcuate field facets 18 has along facet extent in the x-direction and a short facet extent in they-direction. An intermediate space 45 which changes constantly and inparticular strictly monotonically is produced in the embodimentaccording to FIGS. 14 and 15 along the long facet extent, in other wordsalong the x-direction between the two field facets 18 ₁, 18 ₂ which aretilted with respect to one another and adjacent over their long facetextent. In the embodiment according to FIGS. 14 and 15, the intermediatespace 45 between the two field facets 18 ₁, 18 ₂ reduces from the leftto the right. In the case of other directly adjacent field facets 18 ofthe field facet mirror 6 according to FIGS. 14 and 15, the intermediatespace 45 between these field facets 18 may also increase. In theindividual case, directly adjacent field facets 18 in the embodiment ofthe field facet mirror 6 according to FIGS. 14 and 15 may also beconfigured with respect to one another about their respective centres 27a without a relative tilt Z. In this case, the intermediate space 45 mayalso remain constant from the left to the right along the long facetextent.

The tilt angles tilt Z about the tilting axes 26 through the respectivecentres 27 a are located absolutely in the range of −3° to 3°.

One pupil facet of the pupil facet mirror 7 of the illumination optics10 is rigidly allocated to each of the 299 field facets 18 of the fieldfacet mirror 6 according to FIGS. 14 and 15 via an illumination channel.The pupil facet mirror 7 is a transmission facet mirror and the pupilfacets of the pupil facet mirror 7 are transmission facets. Thisallocation is such that a tilting of the image, caused by imaging, ofthe respective field facet 18 in the object field 9 is just compensatedbecause of the respective tilting angle tilt Z about the tilting axis26, which is defined by the respective centre 27 a, of the field facet18, so the images of the field facets 18 superimpose one anotherpractically untilted in the object field 9 despite the tilting imagingeffect of the following optics 8.

A further configuration of a field facet mirror 6 with field facets 18respectively tilted with respect to one another individually about atilt Z is described below with the aid of FIGS. 16 and 17. Components,functions and production method steps, which correspond to those whichwere already described above with reference to FIGS. 1 to 15, have thesame reference numerals and will not be discussed again in detail.

The field facet mirror 6 according to FIGS. 16 and 17, except for thefact that the field facets 18 in the field facet mirror according toFIGS. 16 and 17 are not curved, but have rectangular reflection surfaces22, corresponds to the field facet mirror 6 according to FIGS. 14 and15. The field facet mirror 6 according to FIGS. 16 and 17 also has 299field facets 18, which are individually tilted in each case about a tiltZ, to which, in accordance with the tilting effect of the imaging viaillumination channels, pupil faces of the pupil facet mirror 7 of theillumination optics 10 are individually allocated.

In the field facet mirror 6 according to FIGS. 16 and 17, the packingdensity of the field facets 18 is 53%.

With the aid of FIG. 18, further embodiment of an illumination optics 10will be described below with a field facet mirror 6 and a transmissionfacet mirror in the form of a pupil facet mirror. Components, functionsand production method steps, which correspond to those which werealready discussed above with reference to FIGS. 1 to 17, have the samereference numerals and will not be discussed again in detail.

FIG. 18 shows the superimposition of images of selected illuminationpoints AP on the arcuate field facets 18 of the field facet mirror 6 inthe manner of FIG. 2 in a diaphragm plane or target superimpositionplane, which is described in more detail below, adjacent to the objectfield 9 and spaced apart from the object field 9. The same grid ofillumination points AP is observed on each of the field facets 18 here,specifically an 11×3 grid of three rows equally spaced apart in they-direction each of 11 illumination points AP spaced apart in thex-direction. The spacing of the illumination points AP in thex-direction is selected such that, in the object field 9, an equidistantgrid of the images of the illumination points AP is produced.

In the illumination optics 10, which leads to the superimpositionaccording to FIG. 18, the transmission facets, in other words the pupilfacets of the pupil facet mirror 7, are oriented such that the centres27 a of the reflection surfaces 22 of the arcuate field facets 18 arenot imaged on one point, but on an extended region 46 (cf. FIG. 18). Thecentre 27 a is in each case the point which is located halfway betweenthe intersections of the respective symmetry radii with the side walls27, 28 of the respective reflection surface 22.

FIG. 19 shows the extended imaging region in the centre of the objectfield in a greatly enlarged view. The region 46 has an extent in thex-direction of a few millimeters and an extent of less than onemillimeter in the y-direction. The centre images B(27 a) of the centralillumination points AP are present scattered in the region 46. Thisscattering is the result of a corresponding translation of therespective images of the field facets 18, which is caused by acorresponding tilting of the pupil facets in the x- and y-direction.

The individual x- and y-translation by corresponding tilting adjustmentof the pupil facets means that a total superimposition of all the fieldfacets in the object field 9, in particular at the field edges in thecase of small and large x-values is significantly improved compared toan adjusting specification, in which all the centre images B(27 a) aresuperimposed in a point in the object field 7.

The individual translation in the x- and y-direction, is optimised inthe illumination optics 10 according to FIGS. 18 and 19 in such a waythat the images of the reflection surfaces 22 of the field facets 18along the lower edge 47 in FIG. 18 extending along the long field extentx, are imaged more sharply superimposing one another than along theopposing edge 48 along the long field extent, in other words along thex-axis. From the edge 47 via the use, for example, of a plurality offinger diaphragms, an illumination angle-independent intensitycorrection of the illumination of the object field 9 is possible in theobject plane 11 or in the diaphragm plane spaced apart therefrom, forexample via a UNICOM known from EP 0 952 491 A1. A diaphragm plane of acorrection diaphragm may be spaced apart from the object plane 11, asalready mentioned above. In this case, the optimisation in theillumination optics 10 according to FIGS. 18 and 19 may take place bytranslation in the x- and y-direction such that the images of thereflection surfaces 22 of the field facets 18 along the edge 47 areimaged sharply superimposing one another in the image plane.

The illumination optics 10 according to FIGS. 18 and 19 thereforerepresents a further possibility for compensating a tilting imagingeffect of the following optics 8 by a corresponding configuration of theillumination optics 10 in such a way that, in the object field 7, goodsuperimposition of the field facet images and therefore an optimisedillumination is ensured.

Owing to the arrangement variants described above of the field facets 18of the field facet mirror 6, a transfer of the illumination light 3which was reflected to illuminate the object field 9 by the field facetmirror 6, is maximised.

To produce a microstructured or nanostructured component, the projectionexposure apparatus 1 is used as follows: firstly, the reticle and thewafer are provided. A structure on the reticle is then projected onto alight-sensitive layer of the wafer with the aid of the projectionexposure apparatus 1. By developing the light-sensitive layer, amicrostructure on the wafer and therefore the microstructured component,is produced.

The projection exposure apparatus 1 is designed as a scanner. Thereticle is continuously displaced here in the y-direction during theprojection exposure. Alternatively, a configuration as a stepper is alsopossible, in which the reticle is displaced step-wise in they-direction.

In the arrangement according to FIG. 7, a tilting adjustment, forexample of the field facet 18 ₂ about the centre 30 ₂ is possible,without the other field facets 18 ₁, 18 ₃, 18 ₄ having to be displacedhere.

What is claimed is:
 1. An illumination optics, comprising: a field facetmirror comprising a plurality of arcuate field facets, each arcuatefield facet comprising a reflection surface; an optics comprising atransmission facet mirror configured to image the field facets into anobject field during use of the illumination optics, wherein: thetransmission facet mirror comprises a plurality of transmission facets;each field facet is allocated an individually allocated transmissionfacet to image into the object field during use of the illuminationsystem; the transmission facets are oriented so that, during use of theillumination system, centers of the reflection surfaces of the fieldfacets are imaged on an extended region in the center of the objectfield; and the illumination optics is a microlithography illuminationoptics.
 2. The illumination optics of claim 1, wherein: the object fieldhas a long field extent and a short field extent; the reflectionsurfaces have a long facet extent corresponding to the long field extentof the object field; the reflection surfaces has a short facet extentcorresponding to the short field extent; the transmission facets areoriented so that, during use of the illumination optics, centers of thereflection surfaces are imaged on a region extended along the long fieldextent in the center of the object field.
 3. The illumination optics ofclaim 2, wherein the transmission facets are oriented so that, duringuse of the illumination optics, images of the reflection surfaces alongone of the two edges of the object field, which run along one of the twolong field extents, are imaged more sharply superimposed on one anotherthan along the other of these two edges.
 4. An apparatus, comprising: anillumination optics according to claim 1, wherein the apparatus is amicrolithography projection exposure apparatus.
 5. The apparatus ofclaim 4, further comprising a projection optics configured to image theobject field into the image field.
 6. The illumination optics of claim1, wherein the transmission facet mirror comprises a pupil facet mirror.7. The illumination optics of claim 6, further comprising at least onemirror between the pupil facet mirror and the object plane.
 8. Theillumination optics of claim 6, further comprising three mirrors betweenthe pupil facet mirror and the object plane.
 9. The illumination opticsof claim 8, wherein one of the three mirrors comprises a grazingincidence mirror.
 10. A method, comprising: using an illumination opticsaccording to claim 1 to illuminate an object in an object field; andusing a projection optics to project an image of a structure of theobject to an image field.
 11. An illumination optics, comprising: afield facet mirror comprising a plurality of field facets, each fieldfacet comprising a reflection surface; a pupil facet mirror configuredto image the field facets into an object field during use of theillumination system during use of the illumination optics, wherein: thepupil facet mirror comprises a plurality of pupil facets; each fieldfacet has a corresponding pupil facet to image into the object fieldduring use of the illumination system; the pupil facets are oriented sothat, during use of the illumination system, centers of the reflectionsurfaces of the field facets are imaged on an extended region in thecenter of the object field; and the illumination optics is an EUVmicrolithography illumination optics.
 12. The illumination optics ofclaim 11, wherein: the object field has a long field extent and a shortfield extent; the reflection surfaces have a long facet extentcorresponding to the long field extent of the object field; thereflection surfaces has a short facet extent corresponding to the shortfield extent; the transmission facets are oriented so that, during useof the illumination optics, centers of the reflection surfaces areimaged on a region extended along the long field extent in the center ofthe object field.
 13. The illumination optics of claim 12, wherein thetransmission facets are oriented so that, during use of the illuminationoptics, images of the reflection surfaces along one of the two edges ofthe object field, which run along one of the two long field extents, areimaged more sharply superimposed on one another than along the other ofthese two edges.
 14. The illumination optics of claim 11, furthercomprising at least one mirror between the pupil facet mirror and theobject plane.
 15. The illumination optics of claim 14, furthercomprising three mirrors between the pupil facet mirror and the objectplane.
 16. The illumination optics of claim 15, wherein one of the threemirrors comprises a grazing incidence mirror.
 17. An apparatus,comprising: an illumination optics according to claim 11, wherein theapparatus is an EUV microlithography projection exposure apparatus. 18.The apparatus of claim 17, further comprising a projection opticsconfigured to image the object field into the image field.
 19. A method,comprising: using an illumination optics according to claim 11 toilluminate an object in an object field; and using a projection opticsto project an image of at least a portion of the object to an imagefield.
 20. An illumination optics, comprising: a field facet mirrorcomprising a plurality of field facets, each field facet comprising areflection surface; an optics comprising a transmission facet mirrorconfigured to image the field facets into an object field during use ofthe illumination optics, wherein: the transmission facet mirrorcomprises a plurality of transmission facets; each field facet has acorresponding transmission facet to image into the object field duringuse of the illumination system; the transmission facets are oriented sothat, during use of the illumination system, centers of the reflectionsurfaces of the field facets are imaged on an extended region in thecenter of the object field; and the illumination optics is amicrolithography illumination optics.